Cutting inserts are well known and a large percentage of them are of the throw away design. Such inserts are detachably clamped on a holder and then are discarded when they become dull or chipped. Throw away inserts are usually indexible and often reversible so that an insert can be provided with at least two cutting edges for selective presentation to the cutting position.
The provision of two or more cutting edges on the insert makes it economical to use and is particularly important with respect to throw away inserts because of the high cost of the materials from which the inserts are produced, especially when the material is, for example, a cemented metal carbide.
The inserts must be securely and accurately held in place within an insert holder during the cutting operation. This is especially true when the inserts are employed with numerically controlled machines which depend for accuracy upon an accurately located and firmly supported insert. When the inserts are of a substantial area, it is possible to fix the insert both accurately and firmly within the pocket of a toolholder by providing the insert with a central hole and the toolholder with a pin-type clamping device. In other cases, such inserts may be held in place by a top clamp. Examples of such holders are found in U.S. Pat. Nos. 3,754,309; 3,399,442, 3,762,005 and 4,834,592 and British Patent Specification No. 1,363,542.
The main object of metal machining is the shaping of the new work surface. Much attention is paid to the formation of the chip during the machining process, even though the chip is a waste product. This is because the consumption of energy occurs mainly in the formation and movement of the chip. Thus an essential feature of any metalcutting operation is effective chip control. A principal class of chips is the discontinuous chip which has the practical advantage of being easily cleared from the cutting area. While some metals and alloys generate discontinuous chips during cutting operations, many do not. It is therefore very desirable to produce discontinuous chips during a cutting operation, regardless of the metal or alloy of the work piece.
It has been a common practice to place a mechanical chip breaking member between the insert and the clamp securing the insert to the tool in order to provide at least a degree of chip control during the cutting operation. This arrangement presents the obvious drawback of increasing the effective area necessary for metal cutting operations with a given tool.
Because chip control is an important consideration in metal cutting operations, it has been a long standing objective in the art of metal cutting to develop improved chip breaking members for use with tools as well as improved designs for the cutting inserts. One example of a cutting insert with chip breaking capabilities is the cut-grip inserts "GIP" available from ISCAR. The ISCAR insert has a land with a pair of generally parallel, elongated and elevated members which deform the metal chips as they are removed from the work piece. Another example of a cutting insert with features designed to provide chip control is the Econ-o-grove insert manufactured by Valenite Corporation. This insert has parallel side walls extending along a continuous descending wall, floor and back wall of constant radius. Another example of a cutting insert with a chipbreaker style is commercially available from Sandvik and is characterized by a non-continuous front face which may not provide a flat finish to the cut groove in a work piece.
On example of a metal cutting insert which is provided for threading applications and which is configured to facilitate chipbreaking is taught in U.S. Pat. No. 4,360,297, which is assigned to the assignee of the subject invention and which is incorporated herein by reference. U.S. Pat. No. 4,360,297 provides a recess formed along the horizontal surface adjacent the cutting edge. U.S. Pat. No. 4,834,592, which is assigned to the assignee of the present invention, teaches an improved metal cutting insert which is particularly well suited for use in grooving applications. This patented, grooving insert with integral chip control geometry is an improvement to the insert originally taught in U.S. Pat. No. 3,754,309. Likewise, the insert of this invention, a threading insert with integral chip control geometry represents a further improvement to the insert originally taught in U.S. Pat. No. 3,754,309.
It is an object of the invention to provide an insert with improved chip control geometry which results in improved chip breaking capabilities.
It is another object of this invention to provide such an insert with improved chip control characteristics for thread forming operations.
It is yet another object of this invention to provide an improved chip control insert configured to cooperate with a clamping element of an insert toolholder.